I bought a modis last month off eBay and I'm excited like a kid with a new playstation when the moments come along when I can put it to use. I do have prior experience with an early Modis from a prior job and that experience was mostly on the scan tool side of things. I haven't seen a scope since I got out of the local tech school and it's been a couple years since then so I'm on a learning curve with the machine. But, I've been adapting pretty fast and I enjoy working with the Modis. The moments I can use it are too few and far between so it took me a while to really notice something was wrong.
Most recently, I was scoping a throttle position sensor on an 01 Oldsmobile with an ecotec when I noticed all my voltages were a half a volt low. If setup is easy enough, I will back probe the power and ground along with the signal circuit and that's how I noticed all the voltages were off. My ground was at a negative half volt, the signal wire was at zero volts, and, of course, the reference voltage was at four and a half volts. Most of my voltage traces can and have been a little choppy on anything I've been scoping. While I was observing my lines on the scope, the traces suddenly all went up to zero, .5 and five volts where they belonged and those choppy lines went perfectly straight and smooth. Unfortunately, I managed to botch saving a snap shot of the event.
I do have some snap shots saved from a diag on an 04 GMC envoy that's in the ball park of the same behavior of my Modis. There was a throttle position code that I don't remember, But, I scoped two redundant throttle position sensors both before and after to confirm the repair. The problem with the Modis actually turned up in the after repair. My voltage sweep was still within a five volt range, but the low to high signal was from negative two to positive two volts. I made the mistake of thinking that i was looking at the channel one trace with the channel two voltages displayed. Like I said; learning curve. Here's a couple pics for you:
I've also got this off a 98 S10, 4.3 cam sensor. I replaced the distributor last year and the new distributor was loaded with a new cam sensor. Once I found this turn up, I actually installed the cam sensor out of the old distributor and I was left with pretty much the same waveform. The negative spikes were as deep as -8 volts. I'm more and more suspicious that the Modis is lying to me.
So what I need to know is: Has anybody experienced this same failure with their Modis and what did it cost you to have it repaired? The money I spent on this box left me short of enough cash to deal with any expensive repairs so I need to start budgeting for a repair someday. Is there a calibration that I'm missing? How do I calibrate the scope if it's possible? Is there just something else I've been doing wrong the whole time? Any ideas?
Thanks in advance.
Shaun
Most recently, I was scoping a throttle position sensor on an 01 Oldsmobile with an ecotec when I noticed all my voltages were a half a volt low. If setup is easy enough, I will back probe the power and ground along with the signal circuit and that's how I noticed all the voltages were off. My ground was at a negative half volt, the signal wire was at zero volts, and, of course, the reference voltage was at four and a half volts. Most of my voltage traces can and have been a little choppy on anything I've been scoping. While I was observing my lines on the scope, the traces suddenly all went up to zero, .5 and five volts where they belonged and those choppy lines went perfectly straight and smooth. Unfortunately, I managed to botch saving a snap shot of the event.
I do have some snap shots saved from a diag on an 04 GMC envoy that's in the ball park of the same behavior of my Modis. There was a throttle position code that I don't remember, But, I scoped two redundant throttle position sensors both before and after to confirm the repair. The problem with the Modis actually turned up in the after repair. My voltage sweep was still within a five volt range, but the low to high signal was from negative two to positive two volts. I made the mistake of thinking that i was looking at the channel one trace with the channel two voltages displayed. Like I said; learning curve. Here's a couple pics for you:
I've also got this off a 98 S10, 4.3 cam sensor. I replaced the distributor last year and the new distributor was loaded with a new cam sensor. Once I found this turn up, I actually installed the cam sensor out of the old distributor and I was left with pretty much the same waveform. The negative spikes were as deep as -8 volts. I'm more and more suspicious that the Modis is lying to me.
So what I need to know is: Has anybody experienced this same failure with their Modis and what did it cost you to have it repaired? The money I spent on this box left me short of enough cash to deal with any expensive repairs so I need to start budgeting for a repair someday. Is there a calibration that I'm missing? How do I calibrate the scope if it's possible? Is there just something else I've been doing wrong the whole time? Any ideas?
Thanks in advance.
Shaun
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